Modified copolymers of ethylene-alpha olefin carboxylic acids

ABSTRACT

A homogeneous, random interpolymer of ethylene and an alpha-olefinically unsaturated carboxylic acid or ester having a melt flow rate in the range of about 0.1 to about 300 g/10 minutes, as determined by ASTM D-1238 (190° C./2160 g), is improved during its manufacture when made in a substantially constant environment in a stirred autoclave under substantially steady-state conditions of temperature, pressure, and flow rates, said temperature and pressure being sufficient to produce a single phase reaction, using a free-radical initiator, said improvement being obtained by the use of a minor amount of a telogenic modifier in the reaction mixture, the process being further characterized by the use of either, or both, of (a) a temperature which is lower than that which would be required without the presence of the telogen, or (b) a pressure which is higher than that which would be required without the presence of the modifier.

This application is a continuation of application Ser. No. 08/065,510,filed May 20, 1993, now abandoned which is a continuation of abandonedapplication Ser. No. 07/952,484, filed Sep. 28, 1992, which is acontinuation of abandoned application Ser. No. 07/814,239, filed Dec.23, 1991, which is a continuation of abandoned application Ser. No.07/591,580, filed Oct. 2, 1990, which is a divisional of applicationSer. No. 07/316,257, filed Feb. 27, 1989, now U.S. Pat. No. 4,988,781,issued Jan. 29, 1991, which is a continuation-in-part of abandonedapplication Ser. No. 07/044,865, filed Apr. 30, 1987.

FIELD OF THE INVENTION

Modified copolymers of random interpolymers ofethylene/alpha-olefinically unsaturated carboxylic acids or theiresters.

BACKGROUND OF THE INVENTION

High molecular weight, normally solid interpolymers of ethylene andunsaturated carboxylic acids, such as acrylic acid and methacrylic acid,are well known. This present disclosure pertains to such interpolymerswhen made in a continuous manner under steady state conditions inwell-stirred reactors at high pressure and elevated temperature using afree-radical type initiator whereby random, homogeneous interpolymersare made which are substantially of uniform composition, incontradistinction to polymers made under non-steady state conditions orin non-stirred tubular reactors or in batch reactions or innon-telomerized reactions, and in contradistinction to block copolymersor graft copolymers. In particular, the present disclosure pertainsespecially to high molecular weight random interpolymers of ethylene andunsaturated carboxylic acids with improved extrusion stability.

Patents which disclose interpolymerizations of ethylene and unsaturatedcarboxylic acids in a steady state reaction at high pressure and hightemperature in a stirred reactor in the presence of a free-radicalinitiator are, Canadian Pat. No. 655,298 (and its U.S. counterpart U.S.Pat. No. 4,351,931); U.S. Pat. Nos. 3,239,370; 3,520,861; 3,658,741;3,884,857; 3,988,509; 4,248,990; 4,252,924; 4,417,035 and 4,599,392.

U.S. Pat. No. 3,239,370 discloses a random copolymerization of ethylenewith an unsaturated carboxylic acid (e.g., acrylic acid) in a stirredautoclave reactor operated at 16,000 psi. and 210° C. using a peroxideinitiator, the so-formed copolymer being particularly useful as acoating for non-metallic substrates.

U.S. Pat. No. 3,520,861 discloses a substantially homogeneous,compositionally uniform, random copolymer of ethylene/unsaturated acid(e.g., acrylic acid, methacrylic acid or crotonic acid) prepared in acontinuous manner in a stirred autoclave reactor at high pressure andelevated temperature, using a free-radical initiator (such as aperoxide). The temperature of the polymerization is disclosed as beingin the range of about 120° C. to about 300° C., preferably about 150° C.to about 250° C. The pressure of the polymerization is disclosed asbeing in the range of at least 1000, preferably between about 1000-3000atmospheres, esp. between 1100-1900 atmospheres. The process ispreferably operated using a recycle of the unreacted ethylene andcomonomer to which make-up quantities of ethylene and comonomer areadded prior to reinjection into the stirred autoclave.

Canadian Pat. No. 655,298 and its U.S. counterpart (U.S. Pat. No.4,351,931) discloses homogeneous, compositionally uniform, randomcopolymers of ethylene and unsaturated carboxylic acids (e.g., acrylicacid) wherein said copolymer comprises at least about 90% by weight ofethylene with a melt index of 0.01 to 30 g/10 minutes. The copolymersare prepared in a well-stirred reactor at a pressure of at least 1000atmosphere, at 90°-280° C., using a free-radical initiator, whilemaintaining the ratio of monomers (ethylene/acid) in the range of10,000/1 to 50/1 by weight, the process being performed continuously byfeeding monomers in, while removing reaction mixture, and maintaining aconstant reaction environment.

U.S. Pat. No. 3,658,741 discloses homogeneous copolymers of ethylene andunsaturated carboxylic acids and esters, prepared in the presence of atelogen or chain-transfer agent, a free-radical catalyst, a temperaturebetween 100° and 300° C. and a pressure between 100 and 1000atmospheres, using turbulent agitation; the reaction is said to occur inthe vapor phase and produces very low molecular weight emulsifiablecopolymers i.e., waxes.

U.S. Pat. Nos. 3,884,857 and 3,988,509 disclose the preparation ofcopolymers, such as ethylene/acrylic acid copolymers, in a continuous,high pressure, free-radical polymerization process, at 100°-250° C. and1000-2500 atmospheres of pressure.

U.S. Pat. No. 4,248,990 discloses copolymers, e.g., ethylene/acrylicacid copolymers which are said to be distinguished over the randomcopolymers of Canadian Pat. No. 655,298 and of U.S. Pat. No. 3,520,861by virtue of being non-random. This non-randomness is said to be theresult of operating the steady state, high pressure, stirred reactor ata pressure of from 0 to about 500 psi. above, and at a temperature offrom 0°-15° C. above, that needed to maintain a single-phase reactionmixture at the given concentration of copolymer in the reaction mixtureand at the given comonomer content of the polymer. This patent alsoteaches that the temperature and pressure for the phase change from2-phase to single phase, and from non-random to random is dependent onthe particular monomers and ratios of monomers being used.

U.S. Pat. No. 4,252,924 discloses the preparation of non-randomcopolymers, e.g., ethylene/acrylic acid copolymers in at least twoconstant environment stirred autoclaves in series, each using asingle-phase reaction mixture, but where each succeeding autoclave ismaintained at a temperature of at least 30° C. above that of thepreceding autoclave.

U.S. Pat. No. 4,417,035 discloses copolymers having from 1,500 to 20 MFI(melt flow rate) units as measured at 160° C. under 325 g load, i.e.ASTM D-1238 (160° C./325 g). Such polymers have melt flow rates of morethan 350 g/10 minutes when measured in accordance with ASTM D-1238 (190°C./2160 g).

U.S. Pat. No. 4,599,392 discloses homogeneous, random interpolymers,e.g., ethylene/acrylic acid copolymers, prepared in a constantenvironment, steady state reaction mixture using a well-stirredautoclave reactor at continuous single-phase operation, thatnecessitates elevated temperatures and pressures wherein the phaseboundary is exceeded and a molecular weight distribution (MWD) boundaryis reached or surpassed. Narrow molecular weight distributions are saidto be attainable at elevated temperatures and pressure; however, exactor useful molecular "tailoring" capabilities are largely limited by theposition of the phase boundary and the MWD boundary relative to givenreaction temperature and pressure capabilities. This patent isincorporated herein by reference.

Whereas the use of telogens or chain-transfer agents to controlmolecular weights and polymer densities is common in ethylenehomopolymerizations, operators of processes involvinginterpolymerizations of ethylene and unsaturated carboxylic acids arenot inclined to employ chain-transfer agents due to the proclivity ofethylene/carboxylic acid interpolymers to undergo beta-scission duringthe polymerization reaction and thereby form relatively low molecularweight polymers in contradistinction to high pressure low densitypolyethylene (LDPE) homo-polymerization at the same reaction conditions.

If a chain-transfer agent is also introduced into theinterpolymerization reaction, the polymer molecular weight is furtherlowered and even higher pressures and/or lower temperature are requiredfor additional compensation to produce the targeted high molecularweight interpolymer. However higher pressures dictate more energy andlower temperatures sacrifice conversion (production rate), and therebyin the absence of any recognized benefit, utilization of achain-transfer agent is deemed unnecessary and futile for ethylene andunsaturated carboxylic acid interpolymerizations.

We have now found, by operation of the present invention, that it ispossible to utilize a chain-transfer agent (telogen) in ethylene andunsaturated carboxylic acid interpolymerizations to control molecularweight distributions and long chain branching and achieve unexpectedbenefits while maintaining high molecular weights.

SUMMARY OF THE INVENTION

With reference to random interpolymers of ethylene andolefinically-unsaturated organic comonomers prepared in a well-stirredautoclave and in the presence of a free-radical initiator, undersubstantially steady state continuous operation and substantiallyconstant elevated synthesis conditions that surpass the respectivemolecular weight distribution boundary (as described in U.S. Pat. No.4,599,392), it has now been found, surprisingly and unexpectedly, thatsubstantial and useful improvements are possible by telogen utilizationat somewhat reduced reaction temperatures while maintaining orincreasing reaction pressures. Such utilization enables the preparationof single-phase, low gel interpolymers characterized by substantiallynarrow molecular weight distributions (and/or less high molecular weightpolymer fractions) and appreciably reduced levels of long chainbranching. Given these intrinsic modifications, interpolymers withsubstantially improved extrusion stability can be produced which, forexample, in the instance of interpolymers intended for extrusion coatingor coextrusion coating purposes, possess appreciably improved draw-downand those intended for blown film purposes exhibit substantiallyimproved optics.

Thus, in the practice of the present invention the benefits of the useof telogens are obtained by using, in the interpolymerization reactioneither, or both, of (a) a temperature which is lower than that whichwould be required to obtain single phase operation without the presenceof the telogen, or (b) a pressure which is higher than that which wouldbe required to obtain single phase without the presence of the telogen.

DETAILED DESCRIPTIONS OF THE INVENTION

FIG. 1 is presented as a visual aid for relating the present inventiveconcept and is not drawn to scale.

In this disclosure all percents are by weight unless noted otherwise.

In FIG. 1 it is shown that when a chain-transfer agent is introducedinto the reaction mixture, throughout the entire range of synthesisconditions (of temperature and pressure) narrower molecular weightdistributions are obtained relative to non-telomerized synthesis. Also,FIG. 1 shows that telomerized synthesis is characterized by the sametrending exhibited for ordinary, non-telomerized synthesis, i.e., assynthesis conditions are increased, at lower temperatures relative tonon-telomerized synthesis, the polymerization reaction occurs atconditions beyond the phase boundary and non-random range intosingle-phase operation, and ultimately a molecular weight distribution(MWD) boundary is reached and then surpassed.

The extent of temperature reduction to compensate for the use of telogenis limited by the onset of microgels (phase separation) and/ornon-randomness. Moreover, at a constant elevated pressure and constantunreacted gas recycle rate, as telogen or modifier concentration isincreased and reaction temperature is commensurately decreased to allowa constant high (average) molecular weight, the interpolymer willpossess a corresponding narrower molecular weight distribution and/orless high molecular weight polymer fractions (although the avg. mol. wt.is the same).

Conversely, at a constant reduced reaction temperature and constantunreacted gas recycle rate, as telogen or modifier concentration isincreased and reaction pressure is commensurately increased to provide aconstant high (average) molecular weight, the interpolymer will possessa corresponding narrower molecular weight distribution and/or less highmolecular weight polymer fractions.

The effect of reduced reaction temperature is attributable to reducedpost-reactor temperatures which serve to mitigate in-processfree-radical crosslinking (initiated by excess peroxides and/orexcessive thermal history) that in effect broadens the molecular weightdistribution, particularly on the high molecular weight portion of thewhole polymer, and extends branching through a back-biting mechanism."Back-biting" is a term used in the art to signify a result oftenreferred to as "degradative crosslinking" caused by a chain fragmentattaching to another polymer chain.

The effect of increased reaction pressure, which tends to narrow themolecular weight distribution for interpolymerizations above the MWDboundary, is attributed to favorable changes in reaction kinetics andinitiator efficiencies.

Thus the most narrow molecular weight distribution, low gel randominterpolymer will be prepared at the highest available reaction pressureand at about 0°-10° C. above the temperature at which non-randomnessoccurs for a given comonomer concentration and chain-transfer agent.Skilled practitioners, having read this disclosure, will understand thatin these interpolymerizations, certain chain-transfer agents (e.g.,methanol) tend to shift phase-equilibria (the phase boundary) to lowersynthesis conditions due to favorable solubility effects and therebyallow the preparation of interpolymers with even narrower molecularweight distributions (and/or less high molecular weight polymerfractions) and lower levels of long chain branching while maintainingrandomness and low microgel levels. The currently known art alternativeto shifting phase-equilibria to lower synthesis conditions whilemaintaining low microgel levels is to reduce the comonomer concentrationin the reaction zone and thereby in the interpolymer. This alternative,however, serves to actually broaden the molecular weight distributionand substantially reduce adhesion to polar substrates and appreciablydecrease optics, heat seal strength and hot tack strength; theseresults, in the context of the present invention, are adverse results.

Whereas the present inventive concept is perceived as being broadlyapplicable to interpolymers of ethylene and olefinically-unsaturatedorganic comonomers, where ethylene comprises the majority amount of themonomer mixture, it is especially applicable to acrylates,methacrylates, vinyl esters, and olefinically unsaturated carboxylicacids as comonomers. It is most especially applicable, and preferablyused, in preparing polymers of ethylene interpolymerized with acrylicacid or methacrylic acid. The ensuing descriptions reflect thispreference of acrylic acid and methacrylic acid as comonomers.

This disclosure pertains to a process for preparing homogeneous, random,low gel ethylene copolymers with improved extrusion stability,especially improved copolymers of ethylene and carboxylic acidcomonomers. It is an objective of this invention to provide ethylenecopolymers which are particularly well-suited for adhesive, coatingand/or packaging purposes and as extrusion resins. The objectives of thepresent invention are accomplished by preparing, especially, a copolymerof ethylene and 0.1-35 weight percent of an α,β-ethylenicallyunsaturated carboxylic acid (e.g., acrylic acid and methacrylic acid)having a melt index in the range of from about 0.1 to not more thanabout 300 g/10 minutes, preferably not more than about 75 g/10 minutes,most preferably in the range of about 0.5-25 g/10 minutes, measured byASTM D1238E (190° C./2160 gm). The interpolymer contains about 65-99% ofethylene, preferably about 88-99% ethylene and about 0.1-35% of thecomonomer, preferably about 1-12%.

By "homogeneous, random", it is meant that substantially all of thecopolymer molecules have substantially the same chemical compositionalthough their molecular weight can vary, and that the copolymer has aratio of weight percent adjacent acid to total weight percent carboxylicacid in the copolymer less than 0.44 (as determined in accordance withU.S. Pat. No. 4,248,990).

By "low gel", it is meant that the copolymer was prepared substantiallyat single-phase synthesis conditions and has a gel rating less than 2(as determined in accordance with U.S. Pat. No. 4,599,392).

By "narrow molecular weight distribution", it is meant that for aparticular comparison (of equivalent comonomer content and molecularweight) the subject copolymer will have a numerically smallerweight-average molecular weight to number-average molecular weight ratiorelative to the reference copolymer and/or the subject copolymer willhave less high molecular weight polymer fractions as indicated by alower cumulative fractional weight percent at an arbitrarily highmolecular weight fraction for the given copolymer. Molecular weightratios and fractional weight percentages are determined from gelpermeation chromatography analysis which may require an esterificationpretreatment. By "reduced long chain branching", it is meant that thesubject copolymer is comprised of molecules that have statisticallyshorter chain lengths but more branches in contradistinction to acopolymer comprised of molecules with less branches and statisticallylonger chain lengths. While these molecular or statistical branchingvariations are distinct, the varied copolymers may have the same numberof total carbons and carboxylic acid concentration (i.e., the samemolecular weight). Branching characteristics are conveniently determinedby solution intrinsic viscosity analysis.

The copolymers of the present invention combine toughness, flexibilityand chemical resistance with outstanding, inherent extrusion stabilityand reduced microgel levels that allow substantially improved extrusioncoating, injection molding and blown film properties. One of thesurprising attributes of the copolymers of the present invention is thatoutstanding, inherent extrusion stability is obtained with substantiallyimproved draw down for extrusion coating or coextrusion coatingapplications.

Whereas the incorporation of chemical thermal stabilizers may allowimproved extrusion stability as indicated by improved coating webappearance, chemical stabilization tends to appreciably reduce coatingdraw-down performance. Moreover, chemical stabilization as well as poorextrusion stability ofttimes negatively affect the organolepticproperties of the copolymer which is a critical performance criterionfor food packaging. Another significant disadvantage of chemicalstabilization and poor extrusion stability is reduced copolymeradhesiveness due to chemical interference at active sites or alterationof active sites or poor substrate contact due to chemicalincompatibility or surface distortions or oxidative gels.

The substantially improved extrusion stability of the copolymers of thisinvention is due to the accomplished narrow molecular weightdistribution (and/or less high molecular weight polymer fractions) andreduced long chain branching. Copolymers of the current art aregenerally characterized by comparatively broader molecular weightdistributions and excessive long chain branching, and thereby tend toexhibit long residence distributions during extrusion. Given longer heathistories and the high susceptibility of ethylene/carboxylic acidinterpolymers to thermal degradation (as demonstrated by McKinney et al.in U.S. Pat. No. 4,500,664), the final coating, molding or film willinvariably exhibit distortions or flow patterns (such as orange peel,die lines or applesauce) or oxidative gels or poor optical properties ora combination thereof.

The instant copolymers of the present invention with theircharacteristic narrow molecular weight distributions and reduced longchain branching tend to exhibit shorter residence time distributionsduring extrusion due to the ability to resist chain entanglement andavoid substantial flow into die vortexes and dead-spaces whichconstitutes die hold-up and extended heat history. For the current artcopolymers, given die hold-up (long residence time distributions) andsubsequent thermal degradation during extrusion, polymer viscositiesundergo increases which attenuates the tendency towards die hold-up byincreasing the overall average residence time. Accordingly, long purgetimes are also an attribute of the current art copolymers.

While copolymers of the current art prepared at synthesis conditionswell below the phase boundary (i.e., two-phase products) also possessnarrow molecular weight distributions and reduced long chain branching,such copolymers characteristically contain excessive quantities ofmicrogels or "grain" and due to poor homogeneity, such copolymers arefound to exhibit inferior draw down, optics, hot tack, heat sealstrength and adhesion (as described in U.S. Pat. No. 4,599,392).

The copolymers of the present invention are particularly distinguishedfrom the copolymers disclosed in U.S. Pat. No. 4,599,392 by theutilization of chain-transfer agents to accomplish desirably narrowmolecular distributions that are simply not attainable in instanceswhere the available reaction pressure capability has been otherwiseexhausted. In each instance where additional reaction pressure is madeavailable, the introduction of a chain-transfer agent would still allowadditional narrowing within the precepts of the present invention to theextent that post-reactor crosslinking is a factor and reactiontemperature reductions required for compensation and maintenance of highmolecular weights is possible above the range of non-randomness and theoccurrence of microgels. We have found that relative to the copolymersdisclosed in U.S. Pat. No. 4,599,392, substantial narrowing can beaccomplished to allow appreciably improved extrusion stability whilemaintaining good processibility (i.e., extrusion at acceptable motoramperages and die pressures), randomness, high molecular weights and lowgels.

The present invention is also distinguished from the art disclosed inU.S. Pat. No. 4,599,392 within, with the utilization of a chain-transferagent, it provides the option for accomplishing equivalent molecularweight distributions and branching characteristics at substantiallylower synthesis conditions. While lower reaction temperatures reducepolymer conversion (production rate), reaction gas entry temperaturescan be adjusted for compensation and thereby allow the advantage ofreduced reaction pressures and reduced energy costs while stillaccomplishing the desired molecular weight, molecular weightdistribution and branching attributes.

The process of the present invention requires a chain-transfer agent ortelogen which is commonly referred to in ethylene homopolymerization artas a co-reactant since such compounds can participate in the reactionand can be actually consumed by eventually combining in thecopolymerization to form a telomerized copolymer. Broadly, suitabletelogens are low molecular weight hydrocarbons that may contain oxygenand/or nitrogen and may be saturated or unsaturated. Suitable telogenswill have boiling points less than about 220° C. at atmosphericpressure, preferably less than about 175° C. Additionally, suitabletelogens will have chain-transfer constants or coefficients greater thanabout 0.0006. preferably in the range of about 0.002 to about 0.1 asindicated by Erhlich and Mortimer in Advance Polymer Science, vol. 7,pg. 416 (1970). Suitable compounds include, for example, methanol;propane; t-butyl acetate; ethyl acetate; butane; methyl benzoate;2,2,4-trimethylpentane; n-hexane; isobutane; ethanol; propylene;n-heptane; cyclohexane; methylcyclohexane; 1,2-dichlorethane;cyclopentane; acetonitrile; acetic anhydride; isobutylene; n-tridecane;acetone; isopropanol; 4,4-dimethylpentane-1; trimethylamine;tetrahydrofuran; cumene; dioxane; diisobutylene; butene-1; toluene;methyl ethyl ketone; 3-methyl-2-butanone; ethylbenzene; and methylformate and the like. Especially preferred telogens are isobutane,methanol and methyl ethyl ketone. Other effective telogens can be foundamong the chemicals identified generally as alkanes, alkenes, alcohols,ketones, hydrogen, silanes, cyclic hydrocarbons, aromatic hydrocarbons,halogenated hydrocarbons, sulfoxides, ethers, esters, amines, amides,nitriles, anhydrides, furans, aldehydes, cyanates, sulfides, orhydrocarbon derivatives at concentrations ranging from 0.0001% to 10%and up to about 25% in the total feed to the reactor.

The amount of telogen required for a given interpolymerization dependson a number of factors such as reaction temperature and pressure,unreacted gas recycle rate, comonomer concentration, relativereactivity, the telogenicity of the chain transfer agent and thetargeted molecular weight or product melt index. In accordance with thepresent invention, telogen amounts will vary between about 0.1 to 25weight percent of the total feed to the reactor and usually betweenabout 0.5 to 12 weight percent for copolymers intended for extrusionapplications. To provide the preferred homogeneity, steady state,substantially single-phase operation is required and thereby, thetelogen concentration must be maintained substantially constant in thereaction zone once equilibrium is established, preferably varying within10 percent. Since reaction temperature and pressure have substantial andspecific influences on the resultant molecular weight distribution andbranching characteristics, both must also be maintained substantiallyconstant once equilibrium is established, preferably varying within 10percent, and thereby telogen concentration and the copolymer molecularweight must be controlled independent of reaction temperature andpressure, preferably by controlling the telogen injection rate or theunreacted gas recycle (purge) rate or both.

The copolymers of the present invention can be conveniently prepared atreaction pressures from about 18,000 to about 50,000 psi. and at about150° to about 350° C. as long as the phase boundary conditions areappreciably exceeded and the reaction temperature is sufficiently lowenough and/or the reaction pressure is sufficiently high enough to allowthe benefits of telogen utilization. The preferred reactor is acontinuous autoclave with about a 1:1 to about a 16:1 length to diameterratio. The reactor may consist of one or more reaction zone(s) byinstallation of baffling systems common in the art; the reactor may alsobe in series with one or more other reactors and the reactor mayadditionally be provided with one or more comonomer entry point(s) asdescribed in British Pat. No. 1,096,945. When more than one reactionzone is employed as in instances of baffling, the reactor(s) can bemaintained to provide an "intrazone" and/or "interzone" constantenvironment or it is possible to operate in such a manner that agradient of environments exists between and/or within zones and/orreactors as long as the phase boundary conditions are appreciablyexceeded and the benefits of telogen utilization are attainable.

The products of this invention can be prepared with or without the useof additional solvent or hydrocarbons for telogen combinations (i.e.,two or more different chain-transfer agents) and/or as carriers for thecomonomer(s) and/or initiator(s). These products are also useful as baseresins for the preparation of ionic copolymers, known in the art as"ionomers", wherefrom additional improvements in optics, chemicalresistance and hot tack strength are readily obtained. The gels thatoften characterize ethylene/carboxylic acid interpolymers can be of manydifferent shapes, varying sizes and of more than one origin. Forinstance, in accordance with this disclosure, microgels or "grain"(i.e., very small and fine gels) occur due to operating within and/or inclose proximity of a respective phase boundary. Conversely, large gels(i.e., gels >25 microns in diameter) are usually an attribute or theresult of thermal oxidation or degradation which occurs where polymerheat history is excessive, such as in extrusions or melt-blendings.

In this disclosure, for example, the following gel rating is used:

    ______________________________________                                        GEL RATING*                                                                   RATING     CRITERIA                                                           ______________________________________                                        0          No visible gels                                                    1          Very few microgels                                                 2          Some microgels                                                     3          Some microgels, some large gels                                    4          Numerous microgels, some large gels                                5          Numerous microgels, numerous large gels                            6          Severe gels                                                        ______________________________________                                         *Rating according to criteria by visual inspection of blown film samples.

For instances where the microgel content is negligible (due to synthesissufficiently above the respective phase boundary) and oxidative gels arepredominant, actual gel counting was performed.

The following examples are intended to illustrate the embodiments of thepresent invention, however the invention is not limited to theembodiments illustrated.

EXAMPLE 1 (for comparison purposes)

An ethylene/acrylic acid copolymer containing 6.5 percent acrylic acidby weight and having a 5.5 g/10 minute melt index (ASTM D1238E) wasprepared at about 3500-4500 psi. above and about 15°-25° C. above thatof its respective phase boundary. The copolymer for its given acrylicacid concentration and melt index possessed a relatively broad molecularweight distribution (i.e., 7.7 MW_(w) /MW_(n) ratio as determined fromgel permeation chromatography analysis) and relatively high levels oflong chain branching (i.e., an intrinsic viscosity of 8.934 dl/mg asdetermined by solution viscosity analysis). When extrusion coated at a289° C. melt temperature and 85 rpms. screw speed on a Black-Clawsonextrusion coater with a 30:1 L/D and a 25-inch slot die, the copolymerexhibited 14.7 oxidative gels per 345 feet of web and a relatively lowdraw-down speed (i.e., the thinnest coating attainable without webrupture was 1.26 mils).

EXAMPLE 2

Conversely, a 6.5 percent acrylic acid (by weight) copolymer having thesame melt index was prepared with about 1.93 weight percent of the totalreactor feed comprised of isobutane and at about 5500-6500 psi. aboveand about 0°-10° C. above its corresponding phase boundary. Thiscopolymer possessed a narrow molecular weight distribution (i.e., 5.9MW_(w) /MW_(n) ratio) and reduced long chain branching (i.e., ansolution intrinsic viscosity of 3.070 dl/mg). When extrusion coated onthe Black-Clawson at 289° C. melt temperature and 85 rpms. screw speed,this copolymer exhibited 3.0 oxidative gels per 345 web feet and a highdrawdown speed i.e., a coating thickness of 0.70 was successfullyachieved.

Data for the above examples and for additional samples ofethylene-acrylic acid copolymers are shown in the following tables.Whereas Examples 1, 5, and 7 are examples where prior art was used inmaking random copolymers above their respective MWD boundary with lowmicrogel levels. Examples 2, 3, 4, 6, and 8 illustrate the variousembodiments of the present invention where a chain-transfer agent wasemployed to accomplish narrower molecular weight distributions andreduced long chain branching while remaining above respective phaseboundaries.

Additionally, whereas Example 9 is an example of prior art used inmaking non-random copolymers above their respective phase boundary andExample 10 is an example of prior art used in making random copolymersabove their respective phase boundary, Example 11 illustrates anotherembodiment of the present invention where methanol was employed toaccomplish a narrower weight distribution with low microgel levels attemperatures otherwise below the corresponding phase boundary i.e.,methanol effectively shifted phase-equilibria.

In the following Tables I-IV, the example numbers marked with anasterisk contain no telogen and do not represent the presently claimedinvention.

                  TABLE I                                                         ______________________________________                                                         Example 1*                                                                             Example 2                                           ______________________________________                                        INTRINSIC PROPERTIES                                                          Percent Acrylic Acid ±0.25                                                                    6.5        6.5                                             Melt Index g/10 min. ±0.25                                                                    5.35       5.35                                            MWw/MWn (GPC)*     7.7        5.9                                             Intrinsic Viscosity, dl/mg                                                                       8.934      3.070                                           SYNTHESIS CONDITIONS                                                          Percent Isobutane in feed                                                                        0.0        1.93                                            Synthesis Temperature Above                                                                      15-25       0-10                                           Phase Boundary (°C.)                                                   Synthesis Pressure Above                                                                          0-500     1500-2500                                       MWD Boundary (psi)                                                            EXTRUSION PROPERTIES                                                          Oxidative Gels (per 345 web                                                                      14.7       3.0                                             feet)                                                                         Percent MI Reduction                                                                             20.0       6.0                                             Flow Pattern Count 2          1                                               Total Flow Pattern Width (in)                                                                    0.5        0.5                                             Minimum Coating Thickness at                                                  315° C. extrusion temp (mils)                                                             1.26       0.70                                            Relative Extrusion Stability                                                                     18.5       1.05                                            ______________________________________                                                         Example 3                                                                              Example 4                                           ______________________________________                                        INTRINSIC PROPERTIES                                                          Percent Acrylic Acid ±0.25                                                                    6.5        6.5                                             Melt Index g/10 min. ±0.25                                                                    5.35       5.35                                            MWw/MWn (GPC)*     5.6        5.3                                             Intrinsic Viscosity, dl/mg                                                                       2.959      2.110                                           SYNTHESIS CONDITIONS                                                          Percent Isobutane in feed                                                                        2.88       3.70                                            Synthesis Temperature Above                                                                      15-25       0-10                                           Phase Boundary (°C.)                                                   Synthesis Pressure Above                                                                         3500-4500  3500-4500                                       MWD Boundary (psi)                                                            EXTRUSION PROPERTIES                                                          Oxidative Gels (per 345 web                                                                      0.0        1.8                                             feet)                                                                         Percent MI Reduction                                                                             6.0        --                                              Flow Pattern Count 1          1                                               Total Flow Pattern Width (in)                                                                    0.125      0.5                                             Minimum Coating Thickness at                                                                     0.78       0.57                                            315° C. extrusion temp (mils)                                          Relative Extrusion Stability                                                                     0.58       0.51                                            ______________________________________                                         GPC refers to gel permeation chromatography used to determine molecular       weight distributions.                                                         Extrusions were performed on a 30:1 L/D BlackClawson extrusion coater         equipped with a 24 in. slot die operating at 85 rpms screw speed and          286° C. melt temp.                                                     MI Reduction refers to the difference between the melt index measured         before and after extrusion (in accordance with ASTM D1238E). Lower values     are indicative of improved extrusion stability i.e., resistance to            crosslinking.                                                                 Flow Patterns appear in film or coatings as continuous bands of               "applesauce" or "orange peel". Higher values for width and/or total numbe     indicate inferior web quality or poor extrusion stability.                    Minimum Coating Thickness is the thinnest coating achieveable prior to we     rupture. Lower values are indicative of superior drawdown and improved        extrusion stability.                                                          Relative Extrusion Stability is calculated from (gels * flow patterns *       total flow pattern width * drawdown). The calculation is provided as a        summarization and lower values indicate improved stability.              

                  TABLE II                                                        ______________________________________                                                         Example 5*                                                                             Example 6                                           ______________________________________                                        INTRINSIC PROPERTIES                                                          Percent Acrylic Acid ±0.25                                                                    3.0        3.0                                             Melt Index g/10 min. ±0.50                                                                    11.1       11.1                                            MWw/MWn (GPC)*     9.3        9.4                                             Weight Percent Polymer                                                        ≧487,000 Mol. Wt. (GPC)                                                                   6.86       5.94                                            SYNTHESIS CONDITIONS                                                          Percent Isobutane in feed                                                                        0.0        1.40                                            Synthesis Pressure Above                                                                         2500-3500  2500-3500                                       Phase Boundary (psi)                                                          Synthesis Temperature Above                                                                      25-35       0-10                                           Phase Boundary (°C.)                                                   EXTRUSION PROPERTIES                                                          Oxidative Gels @ 289° C. (per                                                             9.1        ≦0.9                                     345 web feet)                                                                 Total Flow Patterns @ 315°C.                                                              7.0        1.0                                             Minimum Coating Thickness at                                                                     0.49       0.28                                            289° C. extrusion temp (mils)                                          Relative Extrusion Stability                                                                     31.2       ≦0.25                                    ______________________________________                                         GPC refers to gel permeation chromatography used to determine molecular       weight distributions as well as to perform fractional weight percent          analysis.                                                                     Extrusions were performed on a 30:1 L/D BlackClawson extrusion coater         equipped with a 24 in. slot die operating at 85 rpms screw speed and          289° C. or 315° C. melt temperatures.                           Flow Patterns appear in the film or coatings as continuous bands of           "applesauce" or "orange peel" or as die lines. Higher values indicates        inferior web quality or poor extrusion stability.                             Minimum Coating Thickness is the thinnest coating achieveable prior to we     rupture. Lower values are indicative of superior drawdown and improved        extrusion stability.                                                          Relative Extrusion Stability is calculated from (gels * total flow            patterns * drawdown). The calculation is provided as a summarization and      lower values indicate improved stability.                                

                  TABLE III                                                       ______________________________________                                                         Example 7*                                                                             Example 8                                           ______________________________________                                        INTRINSIC PROPERTIES                                                          Percent Acrylic Acid ±0.25                                                                    6.5        6.5                                             Melt Index g/10 min. ±1.0                                                                     8.8        8.8                                             MWw/MWn (GPC)*     9.8        7.9                                             SYNTHESIS CONDITIONS                                                          Percent Isobutane in feed                                                                        0.0        3.30                                            Synthesis Temperature Above                                                   Phase Boundary (°C.)                                                                      22-32      0-10                                            Synthesis Pressure Above                                                      MWD Boundary (psi) 500-1500   500-1500                                        EXTRUSION PROPERTIES                                                          Total Flow Pattern Width at                                                                      6.0        2.0                                             85 rpm (in)                                                                   Total Flow Pattern Width at                                                                      6.0        3.0                                             40 rpm (in)                                                                   Minimum Coating Thickness at                                                                     0.41       <0.31                                           289° C. extrusion temp (mils)                                          Relative Extrusion Stability                                                                     14.8       1.9                                             ______________________________________                                         GPC refers to gel permeation chromatography used to determine molecular       weight distributions.                                                         Extrusions were performed on a 30:1 L/D BlackClawson extrusion coater         equipped with a 24 in. slot die operating at 40 or 85 rpms screw speed an     286° C. melt temp.                                                     Flow Patterns appear in film or coatings as continuous bands of               "applesauce" or "orange peel". Higher values for width and/or total numbe     indicate inferior web quality or poor extrusion stability.                    Minimum Coating Thickness is the thinnest coating achieveable prior to we     rupture. Lower values are indicative of superior drawdown and improved        extrusion stability.                                                          Relative Extrusion Stability is calculated from (gels * total flow patter     width at 85 rpms * total flow pattern width at 40 rpms * drawdown). The       calculation is provided as a summarization and lower values indicate          improved stability.                                                      

                  TABLE IV                                                        ______________________________________                                                      Example  Example  Example                                                     9*       10*      11                                            ______________________________________                                        INTRINSIC PROPERTIES                                                          Percent Acrylic Acid ±0.70                                                                 9.7        9.7      9.7                                       Melt Index g/10 min. ±1.1                                                                  4.1        4.1      4.1                                       MWw/MWn (GPC)*  6.8        9.6      6.6                                       Weight percent Polymer                                                                        4.56       3.28     3.24                                      ≧481,000 Molt. Wt. (GPC)                                               Randomness      non-       random   random                                                    random                                                        SYNTHESIS                                                                     CONDITIONS                                                                    Percent Methanol in feed                                                                      0.0        0.0      2.9                                       Synthesis Pressure Above                                                                      ((3500-4500))                                                                            3500-    3500-                                     MWD Boundary (psi)         4500     4500                                      Synthesis Temperature                                                                          (5-15)     (0-10)   0-10                                     Below Phase Boundary (°C.)                                             BLOWN FILM                                                                    PROPERTIES                                                                    Gel Rating      1.5        4.75     2.0                                       Percent Film Haze                                                                             6.64       6.69     3.47                                      20 Degree Film Gloss                                                                          28.6       32.1     55.0                                      45 Degree Film Gloss                                                                          59.9       63.7     74.7                                      Relative Extrusion                                                                            11.3       33.2     5.4                                       Stability                                                                     ______________________________________                                         () connotes above the phase boundary and (()) connotes below the MWD          boundary.                                                                     GPC refers to gel permeation chromatography used to determine molecular       weight distributions as well as to perform fractional weight percent          analysis.                                                                     Randomness is defined as having a ratio of weight percent adjacent acid t     total weight percent carboxylic acid in the copolymer less than 0.44 as       determined in accordance with U.S. Pat. No. 4,248,990.                        Blown film was prepared at 204° C. on a 24:1 L/D NRM film unit at      2.25 BURand 1.5 mils.                                                         Film haze and gloss determinations were performed in accordance with ASTM     higher gloss values and lower haze values are indicative of superior film     optics and improved extrusion stability.                                      Relative Extrusion Stability is calculated from [(gel rating * haze)/(20      45 gloss) * 100]. The calculation is provided as a summarization and lowe     values indicate improved stability.                                      

We claim:
 1. A random, homogeneous, single-phase interpolymer producthaving a melt flow rate in the range of about 0.1 to about 300 g/10minutes. as determined by ASTM D-1238 (190° C./2160 g), comprising about65% to about 99% by weight of ethylene monomer, the remaining percentagecomprising (a) at least one olefinically-unsaturated comonomer selectedfrom the group consisting of unsaturated carboxylic acids, and (b) aminor amount of a telogenic modifier, said interpolymer being furthercharacterized as having product improvements over those achievablewithout the presence of said telogenic modifier, which is at least oneselected from the group consisting of alkanes, alkenes, alcohols,ketones, hydrogen, silanes, cyclic hydrocarbons, aromatic hydrocarbons,halogenated hydrocarbons, sulfoxides, ethers, esters, amines, amides,nitriles, anhydrides, furans, aldehydes, cyanates, or sulfides, atconcentrations from about 0.0001 weight % to about 10 weight %, saidproduct improvements being further characterized by the product havingless long chain branching and either narrower molecular weightdistribution or less high molecular weight polymer fractions or bothnarrower molecular weight distribution and less high molecular weightpolymer fractions where less high molecular weight polymer fractions areindicated by lower cumulative fractional weight percent at a highmolecular weight fraction, and wherein said interpolymer product has agel rating less than
 2. 2. The product of claim 1 wherein thecopolymerizable olefinically-unsaturated comonomer comprises acrylicacid or methacrylic acid.
 3. The product of claim 1 wherein thecopolymerizable olefinically-unsaturated comonomer is acrylic acid. 4.The product of claim 1 wherein the copolymerizableolefinically-unsaturated comonomer is methacrylic acid.
 5. The productof claim 1 wherein the modifier comprises one or more alkanes.
 6. Theproduct of claim 1 wherein the modifier comprises an alcohol.
 7. Theproduct of claim 1 wherein the modifier is isobutane.
 8. The product ofclaim 1 wherein the modifier is methanol.
 9. A random, homogeneous,single-phase interpolymer product having a melt flow rate in the rangeof about 0.1 to about 300 g/10 minutes, as determined by ASTM D-1238(190° C./2160 g), comprising about 65% to about 99% by weight ofethylene monomer, the remaining percentage comprising (a) at least oneolefinically-unsaturated comonomer selected from the group consisting ofunsaturated carboxylic acids, and (b) a minor amount of a telogenicmodifier, said interpolymer being further characterized as havingproduct improvements over those achievable without the presence of saidtelogenic modifier, which is at least one selected from the groupconsisting of alkanes, alkenes, alcohols, ketones, hydrogen, silanes,cyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons,sulfoxides, ethers, esters, amines, amides, nitriles, anhydrides,furans, aldehydes, cyanates, or sulfides, at concentrations from about0.0001 weight % to about 10 weight %, said product improvements beingfurther characterized by the product having either narrower molecularweight distribution or less high molecular weight polymer fractions orboth narrower molecular weight distribution and less high molecularweight polymer fractions where less high molecular weight polymerfractions are indicated by lower cumulative fractional weight percent ata high molecular weight fraction, and wherein said interpolymer producthas a gel rating less than
 2. 10. The product of claim 9 wherein thecopolymerizable olefinically-unsaturated comonomer comprises acrylicacid or methacrylic acid.
 11. The product of claim 9 wherein thecopolymerizable olefinically-unsaturated comonomer is acrylic acid. 12.The product of claim 9 wherein the copolymerizableolefinically-unsaturated comonomer is methacrylic acid.
 13. The productof claim 9 wherein the modifier comprises one or more alkanes.
 14. Theproduct of claim 9 wherein the modifier comprises an alcohol.
 15. Theproduct of claim 9 wherein the modifier is isobutane.
 16. The product ofclaim 9 wherein the modifier is methanol.
 17. A random, homogeneous,single-phase interpolymer product having a melt flow rate in the rangeof about 0.1 to about 300 g/10 minutes, as determined by ASTM D-1238(190° C./2160 g), comprising about 65% to about 99% by weight ofethylene monomer, the remaining percentage comprising (a) at least oneolefinically-unsaturated comonomer selected from the group consisting ofunsaturated carboxylic acids, and (b) a minor amount of telogenicmodifier said interpolymer being further characterized as having productimprovements over those achievable without the presence of saidtelogenic modifier, which is at least one selected from the groupconsisting of alkanes, alkenes, alcohols, ketones, hydrogen, silanes,cyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons,sulfoxides, ethers, esters, amines, amides, nitriles, anhydrides,furans, aldehydes, cyanates, or sulfides, at concentrations from about0.0001 weight % to about 10 weight %, said product improvements beingfurther characterized by the product having less long chain branching,and wherein said interpolymer product has a gel rating less than
 2. 18.The product of claim 17 wherein the copolymerizableolefinically-unsaturated comonomer comprises acrylic acid or methacrylicacid.
 19. The product of claim 17 wherein the copolymerizableolefinically-unsaturated comonomer is acrylic acid.
 20. The product ofclaim 17 wherein the copolymerizable olefinically-unsaturated comonomeris methacrylic acid.
 21. The product of claim 17 wherein the modifiercomprises one or more alkanes.
 22. The product of claim 17 wherein themodifier comprises an alcohol.
 23. The product of claim 17 wherein themodifier is isobutane.
 24. The product of claim 17 wherein the modifieris methanol.